Glutathione S-transferases (GST) are important in the detoxification of xenobiotics, catalyzing the nucleophilic attack by the thiol group of glutathione on the xenobiotic substrate. The pi class has attracted attention among the GSTs for two major reasons: First, because of its marked increase in tumor tissues and the evidence in the literature that it is an important contributor to the development of resistance to certain chemotherapeutic agents. Secondly, because it is the GST with the broadest tissue distribution, with a notable absence in the liver, suggesting this enzyme may engage in other biological roles aside from detoxification in living systems. The overall goal of this proposal is to provide structural insights into the multiple functions of this enzyme. The first aim is to determine the detailed mechanism that accounts for glutathionylation and activation of 1-Cys Peroxiredoxin by glutathione S-transferase pi using protein-protein complex formation and site-directed mutagenesis. The second aim is to characterize the binding site where tocopherol derivatives bind to glutathione S- transferase pi using affinity labeling and site-directed mutagenesis. These studies will provide insight into the several functions of glutathione S-transferase pi. [unreadable] [unreadable]